Ramsey County Ag Column

By Bill Hodous

June 8, 2009

Howdy!!!

Well, here we go again, more rain.  My dewy rain gauge showed .36 inches of rain at 7:30 am Monday morning.  I have not hear what the rest of the area received.  I checked the NDawn station this morning for GDD’s and the numbers were not good as we already know.  Our units, since the first of May, is at 231.  The normal for this day is 346 GDD’S.  Bare soil temperature this morning indicated 51 degrees and turf soil was at 47.  Hard to get anything to grow with those temps.  Planting has progressed very nicely for many around the county while others have hardly turned a wheel.  I have talked to producers with 90 percent of the tillable acres planted while others will rely heavily on Prevent Plant and those payments will not be that plentiful, for some. 

CORN ROOTWORM SURVIVAL IN FLOODED FIELDS
Although corn rootworms are not typically a problem on our corn grown in North Dakota, there were some questions this past week about how flooded and saturated soil conditions affect corn rootworm survival. The survival of corn rootworms depends on when the flooding occurs and soil temperatures. Research indicates that when saturated soil conditions exist early in the spring, egg survival is not affected by flooding, especially if the flooded water/soil was cool(<50 F). After larvae (Fig. 2) hatch from eggs, typically in mid- to late June in North Dakota, larvae are susceptible to saturated soils, especially in warm conditions (>77 F). Once the larvae dig into the root tissue, they become more tolerant and can survive short durations of saturated soils. Since most of our flooding occurred early in the spring, corn rootworm was in the egg stage. As a result, we can expect little or no mortality due to the flooded soils. If you have a corn rootworm problem use the recommended soil insecticides or Bt corn rootworm hybrids.

ROLLING DRY BEAN AND SOYBEAN GROUND
Over the last few years there has been an increased interest in direct harvesting dry beans. With direct harvest it is important to have the cutter bar as close as possible to the ground. On rocky ground there is a danger that thecombine will hit or pick up a rock, which may cause major damage to expensive equipment or delay the harvest.The objective of rolling dry bean and soybean ground is to push rocks and large soil clods down to the soilsurface and level the soil to allow a low combine cutter bar height during harvest. This will reduce harvest loss bycutting dry bean or soybean stems below pods instead of cutting above or through low pods and leaving seeds in the field. An additional benefit is that at harvest time producers can concentrate on the harvest without feeling the stress of watching for rocks in the field. Dry bean or soybean fields are rolled with large rolling drums after planting, either pre-emergence or post-emergence. The advantages of rolling before the crop has emerged are low potential for plant injury and improved seed-to-soil contact. The disadvantages include increased potential for soil-surface crusting and soil erosion due to wind action. As this planting season is short a lot of activities are taking place at the same time. Although producers may have good intentions to roll the field before emergence other field work or rain may prevent timely rolling of the field. Rolling fields can be done after the crop has emerged, but will potentially cause plant injury including crushed leaves and cracked or broken stems. Plants will die if the stem is broken below the cotyledon leaves, due to loss of all growing points. Injured plants may be more susceptible to lodging and disease. Producers should be careful not to double roll areas of the field as this will cause excessive plant damage and potential compaction.

Dry Bean: Limited research data from Canada (http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/agdex8817) found no significant differences in stand or yield comparing no rolling with rolling after seeding, rolling 3 to 5 days after emergence, or rolling 10 -13 days after emergence. However, there were broken bean hypocotyls arches when beans were rolled 3 to 5 days after emergence. Researchers concluded that the dry beans should be rolled either right after seeding or after the plants have straightened (no hypocotyl arch).

Soybean: NDSU research and farmer testimony indicates that rolling between the cotyledon and first trifoliate stages of soybean should limit injury potential. Also, rolling during the warmest part of the day with less turgid plants may reduce injury potential.

Soybean rolling trials were conducted three years (2001, 2003, and 2004) at the NDSU Carrington

Research Extension Center. There was a trend of plant population decline as rolling was delayed from preemergence to the first or second trifoliate stage. Untreated soybean and pre-emerged rolled soybeans showed no visible injury. Rolling soybeans that had fewer than 50% of the cotyledons emerged, were at the cotyledon stage, or at the first trifoliate stages showed less than 5 percent injury. Early morning rolling of plants at the 3-4 trifoliate stages caused the most visible injury when observed four weeks after rolling as compared to all other treatments. Post-emergence rolling in the afternoon on warmer days is likely to cause less damage to soybeans as the soybeans are less prone to stem breakage compared to early morning when the plant cells are filled with water. Soil conditions, tractor tires, and other factors may also contribute to injury. Soybean seed yield was similar among the unrolled check and rolling treatments. Research results in Minnesota in 2008 (DeJong- Hughes; indicated that soybean plants are somewhat protected from damage if there is previous crop residue on the soil surface. Later rolling caused more plant damage, but rolling did not significantly change soybean yield. Damage to the plants due to the wheel traffic was greater than damage by rolling itself. DeJong-Hughes also found that there is a higher potential for the soil to seal after rolling if adverse rain events take place.

524 4th Ave #5, 2nd Floor Ramsey County Courthouse
Devils Lake  ND  58301
701-662-7027
email - NDSU.Ramsey.Extension@ndsu.edu